Conflicting information about overboarding lath & plaster

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lennyg

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I've been renovating our house for the last 4 months and and am about to tackle the attic rooms. We have a large Victorian detached which previously had 4 attic rooms that we have opened up into one large space. This has resulted in the top part of the roof being just the bare rafters & slate (no membrane) which is open to the purlings. Below this the pitched roof continues to the next purlings which is covered with lath & plaster.

The general advice has been to fill the gaps in the rafters with 50mm foil backed insulation, then add a further layer of insulation ( 70mm) before boarding over. This I can finesse, however what I have conflicting information about is the lath & plaster part of the roof. Is it OK to just overboard direct to the lath & plaster something like 100mm kingspan or similar, then overboard direct to this, or do I need to batten out the lath to a depth of 50mm for ventilation, add the kingspan then batten out this before overboarding or is it more economical to just buy insulated plasterboard and attach that direct to the lath.

All advice greatly appreciated as I have been told various methods and need guidance.
 
lennyg said:
I've been renovating our house for the last 4 months and and am about to tackle the attic rooms. We have a large Victorian detached which previously had 4 attic rooms that we have opened up into one large space. This has resulted in the top part of the roof being just the bare rafters & slate (no membrane) which is open to the purlings. Below this the pitched roof continues to the next purlings which is covered with lath & plaster.

The general advice has been to fill the gaps in the rafters with 50mm foil backed insulation, then add a further layer of insulation ( 70mm) before boarding over. This I can finesse, however what I have conflicting information about is the lath & plaster part of the roof. Is it OK to just overboard direct to the lath & plaster something like 100mm kingspan or similar, then overboard direct to this, or do I need to batten out the lath to a depth of 50mm for ventilation, add the kingspan then batten out this before overboarding or is it more economical to just buy insulated plasterboard and attach that direct to the lath.

All advice greatly appreciated as I have been told various methods and need guidance.
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magnetic boards and big magnets.
 
lennyg said:
I've been renovating our house for the last 4 months and and am about to tackle the attic rooms. We have a large Victorian detached which previously had 4 attic rooms that we have opened up into one large space. This has resulted in the top part of the roof being just the bare rafters & slate (no membrane) which is open to the purlings. Below this the pitched roof continues to the next purlings which is covered with lath & plaster.

The general advice has been to fill the gaps in the rafters with 50mm foil backed insulation, then add a further layer of insulation ( 70mm) before boarding over. This I can finesse, however what I have conflicting information about is the lath & plaster part of the roof. Is it OK to just overboard direct to the lath & plaster something like 100mm kingspan or similar, then overboard direct to this, or do I need to batten out the lath to a depth of 50mm for ventilation, add the kingspan then batten out this before overboarding or is it more economical to just buy insulated plasterboard and attach that direct to the lath.

All advice greatly appreciated as I have been told various methods and need guidance.
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What has the building inspector asked for?
 
We haven't involved building control And I know ripping out is the best option but haven't got the energy to do so. Ideally overboarding is what we'd like to do.
 
lennyg said:
We haven't involved building control And I know ripping out is the best option but haven't got the energy to do so. Ideally overboarding is what we'd like to do.
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We get this a lot on here mate, a lot of people come on to get advice and when they get it they don't take it as it doesn't fit in with what they want.
 
Thanks Stuart. It's not so much not wanting to take the advice it's more that various technical information I've been given conflicts. Kingspan tech support told me I can overboard directly with insulated plasterboard. The superquilt guys told me to batten, add quilt, batten then board, my plasterers just say nothing's a problem. I am just looking for a half decent level of insulation without breaking the bank but don't want to screw up with condensation issues later
 
You will have to find the energy in the future when it's all on the floor cos you never did it properly in the first place might as well have some weetabix one morning and get that energy to pull down
 
I'd read lots of information including elsewhere on this forum that said overboarding was the way to go but I will defer to the knowledge of those that do
 
The foil quilt will have to be battened over to stop it twisting around any screws if you go that way .
 
I suppose I am looking to cut a corner but the gist of my initial question is that the technical information I have been getting conflicts. I take it as a given that the exposed rafters will be done as per previous contributors recommendations, I think what I am actually trying to ascertain is whether I can just put say 100mm foil insulation direct onto the lath & plaster and board that or do I start getting into having to leave 50mm, i.e batten to leave an air gap. As stated previously, Kingspan said I could attach their combined insulated plasterboard direct to the lath & plaster but others have said not.
 
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